Read config from environment and use argparse

Related to https://git.autonomic.zone/decentral1se/xbotlib/issues/7.

xbotlib.py

@@ -1,7 +1,9 @@
 """XMPP bots for humans."""
 
+from argparse import ArgumentParser, BooleanOptionalAction
 from configparser import ConfigParser
 from getpass import getpass
+from os import environ
 from os.path import exists
 from pathlib import Path
 
@@ -39,23 +41,42 @@ class Bot(ClientXMPP):
     CONFIG_FILE = "bot.conf"
 
     def __init__(self):
+        self.parse_arguments()
         self.read_config()
         self.init_bot()
         self.register_xmpp_event_handlers()
         self.register_xmpp_plugins()
         self.run()
 
+    def parse_arguments(self):
+        """Parse command-line arguments."""
+        self.parser = ArgumentParser()
+        self.parser.add_argument(
+            "--input",
+            help="Read configuration from environment",
+            action=BooleanOptionalAction,
+            default=True,
+        )
+        self.args = self.parser.parse_args()
+
     def read_config(self):
         """Read configuration for running bot."""
-        config_file_path = Path(self.CONFIG_FILE).absolute()
-
-        if not exists(config_file_path):
-            self.generate_config()
-
         self.config = ConfigParser()
-        self.config.read(config_file_path)
 
-    def generate_config(self):
+        config_file_path = Path(self.CONFIG_FILE).absolute()
+        if not exists(config_file_path) and self.args.input:
+            self.generate_config_interactively()
+
+        if exists(config_file_path):
+            self.config.read(config_file_path)
+
+        if self.args.input is False:
+            self.read_config_from_env()
+
+        if "bot" not in self.config:
+            raise RuntimeError("Failed to configure bot")
+
+    def generate_config_interactively(self):
         """Generate bot configuration."""
         jid = input("XMPP address (e.g. foo@bar.com): ") or "foo@bar.com"
         password = (
@@ -75,6 +96,14 @@ class Bot(ClientXMPP):
         with open("bot.conf", "w") as file_handle:
             config.write(file_handle)
 
+    def read_config_from_env(self):
+        """Read configuration from the environment."""
+        self.config["bot"] = {}
+        self.config["bot"]["jid"] = environ.get("XBOT_JID")
+        self.config["bot"]["password"] = environ.get("XBOT_PASSWORD")
+        self.config["bot"]["room"] = environ.get("XBOT_ROOM")
+        self.config["bot"]["nick"] = environ.get("XBOT_NICK")
+
     def init_bot(self):
         """Initialise bot with connection details."""
         jid = self.config["bot"]["jid"]